Hi Will,
On 14 April 2014 03:53, Will Deacon will.deacon@arm.com wrote:
On Tue, Mar 18, 2014 at 09:40:57PM +0000, Sebastian Capella wrote:
Use of tracers in local_irq_disable is causes abort loops when called with irqs disabled using a temporary stack. Replace local_irq_disable with raw_local_irq_disable instead to avoid tracers.
Do you have any more information about these aborts? At the time we call local_irq_disable, the stack is still intact, so if the issue is simply related to having any tracers active at the call_with_stack invocation, we'd be better off disabling tracing here altogether.
This is specifically for when soft_restart is called in the hibernation path with tracers enabled. At that point, we've already switched to a temporary stack, and when we call local_irq_disable, we'll see this:
In the local_irq_disable, it ends up calling trace_hardirqs_off (CONFIG_TRACE_IRQFLAGS_SUPPORT is enabled), which calls trace_hardirqs_off_caller which checks lockdep_recursion in the current task, but we've switched to a temporary stack with the call_with_stack, and get_current is returning NULL. This triggers a data abort, which calls trace_hardirqs_off again and so on.
We originally had a patch which added a soft restart called soft_restart_noirq which avoided the irq disable.
You can see the discussion here: https://patchwork.kernel.org/patch/3677591/
Thanks!
Sebastian